Technical Field
The disclosure relates to the camera of a surveillance system. Furthermore, the camera has a rotatable lens module and a light module. In this disclosure, a shading device is installed in the camera that when the lens module and the light module rotate to a preset angle zone, the shading device can shade part of the light emitted by the light module onto the reflective object of the camera.
Description of Related Art
FIG. 1 shows a dome camera used in a surveillance system. It has a rotatable filming module (10) and a rotatable light module (20). The LED (21) of the light module (20) is set around the lens (10) of the filming module. The filming module (10) and the light module (20) are connected to a base frame with a support shaft; the reflective case (26) and the transparent dome cover (27) envelop and fasten the above mentioned 2 modules and the base frame inside.
The light module provides light source to make the images taken by the lens clear. The light module rotates with the filming module. The rotation here means that the filming module and the light module rotate using the support shaft that is connected to the base frame as center. The maximum angle zone of the rotation should be 90 degrees back and froth from the vertical axis Y to the horizontal axis X of the camera.
However, the above mentioned maximum angle zone can not be put into reality. Mainly because that when the filming module and the light module rotate about 60 degrees from the vertical axis Y to the horizontal axis X, a part of the light emit from the LED (21) of the light module (20) will project on the inside of the reflective case (26) and result in non-directional reflected light, which is leaked onto the lens after multiple reflection or via a light conductor such as the dome top (27) and overexposes the images taken. So the images taken between 60 degrees and the horizontal axis X are all overexposed and unclear. For avoiding this problem, the rotating angle of the filming module and the light is set to be less than 60 degrees. Nevertheless, the angle zone limits also the filmable angle zone of the filming module.